A submersible craft explores the largest of the Great Lakes

David Long sounded as excited as a passenger aboard a space shuttle. "It was spectacular," he burbled. "It was like sitting in a big bubble and looking at a movie playing in front of you. We found sheer cliffs, we found pockmarked holes like dimples on a golf ball. And we found these little red marks all over the rocks." Long's exhilaration came not from leaving the earth's surface but from going beneath it, on the first submarine exploration to the bottom of one of the world's biggest bodies of fresh water, Lake Superior.